1. Field of the Invention
This invention relates to an optical block reinforcing member that is used in an optical module to transmit and/or receive optical signals as Ethernet (registered trademark) signal being gigabit-class in signal transmission speed so as to reinforce an optical block connected to an optical connector, the optical block for reducing a pressing force occurred when connecting the optical connector to the optical block, and the optical module composed of the optical block reinforcing member and the optical block.
2. Description of the Related Art
In recent years, the bandwidth of the Internet increases. Especially, Ethernet (registered trademark) spreads as a core technology for domestic LAN and WAN since it is inexpensive and easy in operation.
At present, in Japan, the standardization of 10-gigabit Ethernet (registered trademark) has been completed, where in optical modules mainly for middle-range network the transmission speed is upgraded from 1 Gbit/s to 10 Gbit/s. Also, 40 to 100 Gbit/s class Ethernet (registered trademark) with a transmission speed over 10 Gbit/s has been researched and developed. An example of an optical module used therefor is an optical transceiver using plural semiconductor laser diodes (LD) or photodiodes (PD).
US 2006/0153506A1 discloses, as shown in FIG. 27, an optical module 141 that uses a circuit board 142 as rigid flex board (or a flex rigid printed wiring board).
The circuit board 142 is composed of a sub-board 142s, a main board 142m and a flexible portion 142f connecting the boards. An optical element 143 is mounted on the sub-board 142s, a planar lens 144 is disposed to cover the optical element 143, and the planar lens 144 is attached to the inside front face of MSF (Metal Support Frame) 145. The main board 142m is provided with a card edge connector 146 at the other end and is fixed on the inside bottom face of the MSF. The optical module 141 is used such that the card edge connector 146 side of the circuit board 142 is inserted into a female connector of a host board of a network device such as a switching hub.
In the optical module 141, the flex portion 142f is provided between the planar lens 144 and the main board 142m. Thus, even if the MSF 145 or the circuit board 142 is slightly deformed when inserting the circuit board 142 into the female connector of the host board, stress can be absorbed by the flex portion 142f so that it is not generated at the connection part between the planar lens 144 and the sub-board 142s. 
Further, in the optical module 141, a pressing force F is applied when connecting an optical connector 148 with an optical fiber 147 to the planar lens 144. However, since stress can be absorbed by the flex portion 142f so that it is not generated at the connection part between the planar lens 144 and the sub-board 142s. Thus, in US 2006/0153506A1, it is essential to have the flex portion 142f. 
JP-A-2000-249883 also discloses an optical module using the rigid flex board.
However, the circuit board 142 used by the optical module 141 is formed with a rigid flex board which is more expensive than a normal rigid board.
Therefore, the cost of the optical module 141 must increase so that the low-cost installation as one of the advantages of the Ethernet (registered trademark) will be eliminated.
Until now, no optical module with high reliability has been developed that uses the low-cost rigid board as the circuit board and can prevent stress from being generated at the connection part between the lens and the circuit board.